code: def ref_grad_binary_tanh(x, dy, **kw):
      return (dy * (1 - np.floor(np.minimum(np.abs(x), 1)))).flatten()
  
file_path: nnabla/python/test/function/test_binary_activation.py
imports: import pytest
  import numpy
  import nnabla.functions
  from nbla_test_utils import function_tester, list_ctx_and_func_name
label_desc: Use image node_id 2 for calling a global function with example usage: ref_grad_binary_tanh(x, dy) and returns: unknown